Field of the Invention
The present invention relates to an angle adjustment apparatus of an optical member, and more particularly, to an angle adjustment apparatus used for an image display apparatus.
Description of the Related Art
A projector having liquid crystal panels respectively corresponding to each light of three primary colors (R, G and B) adjusts an angle of an optical functional member (optical member) disposed between each of the liquid crystal panels of the three primary colors and a composite prism to improve optical performance. For example, Japanese Patent Laid-Open No. (“JP”) 2006-39087 adjusts an angle of a phase difference compensation plate disposed between a liquid crystal panel and a composite prism to improve contrast. Additionally, Japanese Patent Laid-Open No. (“JP”) 11-202408 discloses a method tilting a transparent plate-like member disposed between a liquid crystal panel and a composite prism to perform registration adjustment of less than one pixel.
Disposing an angle adjustment mechanism of the optical functional member between the liquid crystal panel and the composite prism requires a space corresponding to a range of movement of the mechanism in addition to a space that the mechanism occupies. Thus, widening a distance between the liquid crystal panel and the composite prism is required to be provided with the angle adjustment mechanism.
In a projection display apparatus (projector), widening the distance between the liquid crystal and the composite prism increases a backfocus of a projection lens, and thus enlargers the projection lens. Accordingly, the angle adjustment mechanism is preferably a small size.
JP2006-39087 performs angle adjustment around one axis regarding a tilt around an axis perpendicular to an optical axis. JP11-202408 also performs angle adjustment by a tilt around one axis. For example, in the angle adjustment according to JP11-202408, an elastic member urges an optical functional member, and thus a tilting fulcrum of the transparent plate-like member is not determined to one. Moreover, in a configuration where the transparent plate-like member is tiltable around orthogonal two axes, tilting the transparent plate-like member around one axis can tilt the transparent plate-like member around the other axis (hereinafter, this phenomenon is referred to as “crosstalk”). Further, the transparent plate-like member can rotate around an axis parallel to an optical axis (hereinafter, rotating the transparent plate-like member around the optical axis is referred to as “rotation”).
Thus, for example, adjusting contrast of a phase difference compensation plate using the angle adjustment mechanism may decrease a peak value of contrast due to “rotation”. In addition, for example, performing registration adjustment using a wavelength plate may reduce contrast due to an unintended rotation of the wavelength plate.